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Halpern DG, Weinberg CR, Pinnelas R, Mehta-Lee S, Economy KE, Valente AM. Use of Medication for Cardiovascular Disease During Pregnancy. J Am Coll Cardiol 2019; 73:457-476. [DOI: 10.1016/j.jacc.2018.10.075] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 10/19/2018] [Accepted: 10/23/2018] [Indexed: 01/03/2023]
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How to Improve Effectiveness and Adherence to Antihypertensive Drug Therapy: Central Role of Dihydropyridinic Calcium Channel Blockers in Hypertension. High Blood Press Cardiovasc Prev 2017; 25:25-34. [PMID: 29197935 PMCID: PMC5842506 DOI: 10.1007/s40292-017-0242-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 11/20/2017] [Indexed: 12/04/2022] Open
Abstract
Essential hypertension is a complex clinical condition, characterized by multiple and concomitant abnormal activation of different regulatory and contra-regulatory pathophysiological mechanisms, leading to sustained increase of blood pressure (BP) levels. Asymptomatic rise of BP may, indeed, promote development and progression of hypertension-related organ damage, which in turn, increases the risk of major cardiovascular and cerebrovascular events. A progressive and independent relationship has been demonstrated between high BP levels and increased cardiovascular risk, even in the high-to-normal range. Conversely, evidence from randomized controlled clinical trials have independently shown that lowering BP to the recommended targets reduces individual cardiovascular risk, thus improving event-free survival and reducing the incidence of hypertension-related cardiovascular events. Despite these benefits, overall rates of BP control remain poor, worldwide. Currently available guidelines support a substantial equivalence amongst various antihypertensive drug classes. However, several studies have also reported clinically relevant differences among antihypertensive drugs, in terms of both BP lowering efficacy and tolerability/safety profile. These differences should be taken into account not only when adopting first-line antihypertensive therapy, but also when titrating or modulating combination therapies, with the aim of achieving effective and sustained BP control. This review will briefly describe evidence supporting the use of dihydropyridinic calcium channel blockers for the clinical management of hypertension, with a particular focus on barnidipine. Indeed, this drug has been demonstrated to be effective, safe and well tolerated in lowering BP levels and in reducing hypertension-related organ damage, thus showing a potential key role for improving the clinical management of hypertension.
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Parumasivam T, Chan JGY, Pang A, Quan DH, Triccas JA, Britton WJ, Chan HK. In Vitro Evaluation of Inhalable Verapamil-Rifapentine Particles for Tuberculosis Therapy. Mol Pharm 2016; 13:979-89. [PMID: 26808409 DOI: 10.1021/acs.molpharmaceut.5b00833] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent studies have demonstrated that efflux pumps of Mycobacterium tuberculosis (M. tb) provide a crucial mechanism in the development of drug resistant to antimycobacterial drugs. Drugs that inhibit these efflux pumps, such as verapamil, have shown the potential in enhancing the treatment success. We therefore hypothesized that the combined inhaled administration of verapamil and a first-line rifamycin antibiotic will further improve the treatment efficacy. An inhalable dry powder consisting of amorphous verapamil and crystalline rifapentine with l-leucine as an excipient was produced by spray drying. The in vitro aerosol characteristic of the powder, its microbiological activity and stability were assessed. When the powder was dispersed by an Osmohaler, the total fine particle fraction (FPFtotal, wt % of particles in aerosol <5 μm) of verapamil and rifapentine was 77.4 ± 1.1% and 71.5 ± 2.0%, respectively. The combination drug formulation showed a minimum inhibitory concentration (MIC90) similar to that of rifapentine alone when tested against both M. tb H37Ra and M. tb H37Rv strains. Importantly, the combination resulted in increased killing of M. tb H37Ra within the infected macrophage cells compared to either verapamil or rifapentine alone. In assessing cellular toxicity, the combination exhibited an acceptable half maximal inhibitory concentration (IC50) values (62.5 μg/mL) on both human monocytic (THP-1) and lung alveolar basal epithelial (A549) cell lines. Finally, the powder was stable after 3 months storage in 0% relative humidity at 20 ± 3 °C.
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Affiliation(s)
- T Parumasivam
- Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia
| | - J G Y Chan
- Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia.,JHL Biotech, Incorporated , Hsinchu 300, Taiwan
| | - A Pang
- Tuberculosis Research Program, Centenary Institute, The University of Sydney , Sydney, New South Wales 2006, Australia
| | - D H Quan
- Infectious Diseases and Immunology, Sydney Medical School, The University of Sydney , Sydney, New South Wales 2006, Australia
| | - J A Triccas
- Infectious Diseases and Immunology, Sydney Medical School, The University of Sydney , Sydney, New South Wales 2006, Australia
| | - W J Britton
- Infectious Diseases and Immunology, Sydney Medical School, The University of Sydney , Sydney, New South Wales 2006, Australia.,Tuberculosis Research Program, Centenary Institute, The University of Sydney , Sydney, New South Wales 2006, Australia
| | - H K Chan
- Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia
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Tocci G, Battistoni A, Passerini J, Musumeci MB, Francia P, Ferrucci A, Volpe M. Calcium channel blockers and hypertension. J Cardiovasc Pharmacol Ther 2014; 20:121-30. [PMID: 25398848 DOI: 10.1177/1074248414555403] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Effective treatment of high blood pressure (BP) represents a key strategy for reducing the burden of hypertension-related cardiovascular and renal diseases. In spite of these well-established concepts, hypertension remains poorly controlled worldwide. In order to improve BP control in patients with hypertension, several interventions have been proposed, among which (1) preferred use of more effective, sustained, and well-tolerated antihypertensive drug aimed to ensure adherence to prescribed medications and (2) extensive use of rational, integrated, and synergistic combination therapies, even as first-line strategy, aimed to achieve the recommended BP targets. Within the possible antihypertensive drug classes currently available for the clinical management of hypertension, both in monotherapy and in combination therapy, drugs inhibiting the renin-angiotensin system and calcium channel blockers (CCBs) have demonstrated to be effective and safe in lowering BP levels and achieving the recommended BP targets with a good tolerability profile. In particular, CCBs have been one of the most widely used classes of antihypertensive agents in the last 20 years, based on their effectiveness in reducing BP levels, good tolerability, and abundant evidence on reducing cardiovascular and renal consequences of hypertension. This article provides an updated overview of the evidence supporting the use of CCBs-based antihypertensive regimen, both in monotherapy and in combination therapies with different classes of antihypertensive drugs.
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Affiliation(s)
- Giuliano Tocci
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome IRCCS Neuromed, Pozzilli (IS), Italy
| | - Allegra Battistoni
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome
| | - Jasmine Passerini
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome
| | - Maria Beatrice Musumeci
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome
| | - Pietro Francia
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome
| | - Andrea Ferrucci
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome
| | - Massimo Volpe
- Division of Cardiology, Department of Clinical and Molecular Medicine, Faculty of Medicine and Psychology, University of Rome Sapienza, Sant'Andrea Hospital, Rome IRCCS Neuromed, Pozzilli (IS), Italy
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Yang S, Lee YS, Oh E. Pharmacokinetics of drugs in spontaneously or secondary hypertensive rats. Xenobiotica 2013; 44:77-88. [PMID: 23808362 DOI: 10.3109/00498254.2013.809616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
1. Spontaneously hypertensive rats (SHRs) and deoxycorticosterone acetate-salt-induced hypertensive rats (DOCA-salt rats) have been developed as animal models for human essential (idiopathic or primary) and secondary hypertensions, respectively. 2. In order to identify pharmacokinetic changes (mainly non-renal clearance, CLNR) in 16-week-old SHRs due to hereditary characteristics and/or neither the hypertensive state itself, we reviewed the pharmacokinetics of drugs in 6- (blood pressure within a normotensive range) and 16-week-old SHRs and 16-week-old DOCA-salt rats compared with respective control rats. 3. We reviewed changes in CLNRs of drugs which are primarily metabolized via hepatic microsomal cytochrome P 450 enzymes (CYPs) based mainly on data from hypertensive rats, and present the data in terms of changes in in vitro hepatic intrinsic clearance (CLint), free fraction in plasma (fp) and hepatic blood flow rate (QH) depending on the hepatic excretion ratios of drugs. In general, changes in the CLNRs of drugs in this category were well-explained by the above-described factors. 4. We also reviewed and discussed the mechanism of urinary excretion of drugs (i.e. glomerular filtration and active renal secretion or reabsorption) in hypertensive rats.
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Affiliation(s)
- Sihyung Yang
- Department of Pharmaceutical Chemistry, The University of Kansas , Lawrence, KS , USA
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Wagner C, Thelen K, Willmann S, Selen A, Dressman JB. Utilizing in vitro and PBPK tools to link ADME characteristics to plasma profiles: case example nifedipine immediate release formulation. J Pharm Sci 2013; 102:3205-19. [PMID: 23696038 DOI: 10.1002/jps.23611] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/22/2013] [Accepted: 04/23/2013] [Indexed: 11/12/2022]
Abstract
One of the most prominent food-drug interactions is the inhibition of intestinal cytochrome P450 (CYP) 3A enzymes by grapefruit juice ingredients, and, as many drugs are metabolized via CYP 3A, this interaction can be of clinical importance. Calcium channel-blocking agents of the dihydropyridine type, such as felodipine and nifedipine, are subject to extensive intestinal first pass metabolism via CYP 3A, thus resulting in significantly enhanced in vivo exposure of the drug when administered together with grapefruit juice. Physiologically based pharmacokinetic (PBPK) modeling was used to simulate pharmacokinetics of a nifedipine immediate release formulation following concomitant grapefruit juice ingestion, that is, after inhibition of small intestinal CYP 3A enzymes. For this purpose, detailed data about CYP 3A levels were collected from the literature and implemented into commercial PBPK software. As literature reports show that grapefruit juice (i) leads to a marked delay in gastric emptying, and (ii) rapidly lowers the levels of intestinal CYP 3A enzymes, inhibition of intestinal first pass metabolism following ingestion of grapefruit juice was simulated by altering the intestinal CYP 3A enzyme levels and simultaneously decelerating the gastric emptying rate. To estimate the in vivo dispersion and dissolution behavior of the formulation, dissolution tests in several media simulating both the fasted and fed state stomach and small intestine were conducted, and the results from the in vitro dissolution tests were used as input function to describe the in vivo dissolution of the drug. Plasma concentration-time profiles of the nifedipine immediate release formulation both with and without simultaneous CYP 3A inhibition were simulated, and the results were compared with data gathered from the literature. Using this approach, nifedipine plasma profiles could be simulated well both with and without enzyme inhibition. A reduction in small intestinal CYP 3A levels by 60% was found to yield the best results, with simulated nifedipine concentration-time profiles within 20% of the in vivo observed results. By additionally varying the dissolution input of the PBPK model, a link between the dissolution characteristics of the formulation and its in vivo performance could be established.
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Affiliation(s)
- Christian Wagner
- Institute of Pharmaceutical Technology, Goethe University, 60438 Frankfurt am Main, Germany
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7
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Andersson KE. Calcium-entry blockers. A heterogeneous family of compounds. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 694:142-52. [PMID: 3890469 DOI: 10.1111/j.0954-6820.1985.tb08810.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Hermann P, Morselli PL. Pharmacokinetics of diltiazem and other calcium entry blockers. ACTA PHARMACOLOGICA ET TOXICOLOGICA 2009; 57 Suppl 2:10-20. [PMID: 3904330 DOI: 10.1111/j.1600-0773.1985.tb03570.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Diltiazem, as well as other calcium entry blockers, is widely prescribed for the treatment of various types of angina. This review summarizes the current state of knowledge of the pharmacokinetics of diltiazem and of two other calcium entry blockers: verapamil and nifedipine. Although unrelated in their chemical structure, these three drugs have common features. They are highly lipophilic and have a large volume of distribution, are mainly cleared by metabolism and undergo an extensive first-pass extraction. On the other hand, as expected from their quite dissimilar structures, they have their own particular kinetic characteristics. For example, metabolism of diltiazem and verapamil gives rise to active metabolites; repeated administration influences the kinetic profile of verapamil but not those of diltiazem and nifedipine. Absorption, distribution and elimination of these three drugs are differently affected by age and pathological conditions. The possible drug interactions involving diltiazem and the other calcium entry blockers are discussed, particularly that with digoxin. Due to its large therapeutic index, there is no need for treatment monitoring of diltiazem. Nevertheless, this procedure may provide useful information for optimizing the dosage regimen of each patient as the pathological condition and drug therapy may be quite complex.
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Popović J. Validation of the hepatic blood flow rate model for verapamil first-pass metabolism. Eur J Drug Metab Pharmacokinet 2007; 32:13-9. [PMID: 17479539 DOI: 10.1007/bf03190985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The bioavailability of a new retard tablet formulation of verapamil was investigated in a randomized cross-over bioequivalence study on 12 healthy subjects. The drug was given in the form of a single 240-mg oral dose of a new retard tablet formulation, or as a standard retard tablet at the same dose to all subjects, followed by a single intravenous (i.v.) dose of 5 mg to 8 of the 12 subjects. Plasma verapamil concentrations were determined by a high performance liquid chromatography (HPLC) method. The bioavailability of the new peroral retard formulation was (20.00 +/- 4.30)% and was in reasonable agreement with that determined for the already registered verapamil retard formulation, i.e. (19.46 +/- 4.02)%, thereby indicating bioequivalence. For the prediction of systemic availability and estimation of the first-pass metabolism, only based on the data for peroral plasma levels, a hepatic blood flow rate limited model was used. In our experience, this model has been found to be extremely useful in providing reasonable estimates of verapamil first-pass effect.
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Affiliation(s)
- Jovan Popović
- Department of Pharmacology, Toxicology and Clinical Pharmacology, Faculty of Medicine, Novi Sad, Republic of Serbia
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Theodore LJ, Nelson WL. Synthesis of deuterated optically active verapamil and gallopamil, and of N-13C-methyl-verapamil. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.2580241007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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11
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12
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Nelson WL, Bartels MJ. Deuteration of verapamil by acid catalyzed exchange. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.2580210211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Popović J, Mitić R, Sabo A, Mikov M, Jakovljević V, Daković-Svajcer K. Spline functions in convolutional modeling of verapamil bioavailability and bioequivalence. II: Study in healthy volunteers. Eur J Drug Metab Pharmacokinet 2006; 31:87-96. [PMID: 16898076 DOI: 10.1007/bf03191124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The pharmacokinetics of a new verapamil retard tablet formulation have been investigated in a randomized cross-over bioequivalence study on 12 healthy subjects. The drug was given orally at a single new or standard retard tablet dose of 240mg and at a single intravenous dose of 5mg. Plasma verapamil concentrations were determined by HPLC. New retard tablets produced peak plasma verapamil concentrations of 81.34+/-5.69microg/l, time to peak plasma concentrations of 4.91+/-0.89h and an AUC (0-24h) of 1291+/-103.4h x microg/l, with a terminal phase half-life of 55.1+/-14.9h. After intravenous administration verapamil exhibited biphasic elimination kinetics with a terminal plasma half-life of 2.36+/-0.42h and systemic clearance of 34.32+/-5.81 l/h. Bioavailability of the new peroral retard formulation ranged from 19.49+/-4.41% to 67.69+/-11.70%. Absorption rates and amounts were evaluated by means of the spline-convolutional method. Input rates for the new verapamil retard formulation ranged from 0.77+/-0.20mg/h to 5.57+/-1.58mg/h. The cumulative amount of verapamil input was 39.17+/-9.71% for the new retard tablets. All pharmacokinetic parameters for the new verapamil retard tablet formulation, were in reasonable agreement with the data obtained on already registered verapamil retard formulations, indicating their bioequivalence.
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Affiliation(s)
- J Popović
- Faculty of Medicine, Pharmacology Department, Novi Sad, Serbia
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Vertzoni MV, Reppas C, Archontaki HA. Sensitive and simple liquid chromatographic method with ultraviolet detection for the determination of nifedipine in canine plasma. Anal Chim Acta 2006; 573-574:298-304. [PMID: 17723537 DOI: 10.1016/j.aca.2006.03.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 02/15/2006] [Accepted: 03/09/2006] [Indexed: 10/24/2022]
Abstract
An isocratic high-performance liquid chromatographic method with detection at 240 nm was developed, optimized and validated for the determination of nifedipine in canine plasma. Liquid-liquid extraction was used as the sample preparation technique. Carbamazepine was used as internal standard. A Hypersil BDS RP-C18 column (250 mm x 4.6 mm, 5 microm) was equilibrated with a mobile phase composed of water and methanol, 45:55 (v/v). Its flow rate was 1 ml min(-1). The elution time for nifedipine and carbamazepine was approximately 12 and 8 min, respectively. Calibration curves of nifedipine in plasma were linear in the concentration range of 1-200 ng ml(-1). Limits of detection and quantification in plasma were 0.5 and 1.5 ng ml(-1), respectively. Recovery was greater than 98%. Intra- and inter-day relative standard deviation for nifedipine in plasma was less than 8.5 and 10%, respectively. This method was applied to the determination of nifedipine plasma levels after administration of commercially available soft gelatine capsules to dogs.
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Affiliation(s)
- M V Vertzoni
- Laboratory of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, National and Kapodistrian University of Athens, 157 71 Athens, Greece
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Fraile LJ, Bregante MA, Garcia MA, Solans C. Altered diltiazem metabolism in the neonatal rabbit following intra-uterine chronic exposure to diltiazem. Xenobiotica 2001; 31:177-85. [PMID: 11465404 DOI: 10.1080/00498250110043517] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
1. Diltiazem undergoes extensive metabolism in hepatic and extrahepatic tissues. Deacetyldiltiazem (M1) and N-demethyldiltiazem (MA) are two of the main basic metabolites of diltiazem that retain pharmacological activity. This drug impairs its own metabolism after chronic administration in the adult patient. The study examines the possibility that intra-uterine exposure following chronic maternal therapy with DTZ from mid-gestation to term also impairs DTZ metabolism of its offspring. 2. DTZ was incubated in homogenates from liver, lung, brain and gut and in the whole blood of animals whose mothers were exposed to chronic treatment with diltiazem or unexposed (placebo). DTZ and its metabolites were assayed by HPLC. 3. DTZ deacetylase activity observed in liver, lung and brain homogenates from 1-, 8- and 16-day-old rabbits was significant lower in exposed animals. In gut homogenates, this age-dependent effect was not so clear. This inhibition could not be detected in any organ of 30-day-old rabbits. On the other hand, the activity observed in whole blood was not altered by intra-uterine chronic exposure to DTZ. 4. DTZ demethylase activity showed no differences in tissue homogenates and in whole blood from exposed compared with the unexposed rabbit. 5. In conclusion, the findings suggest that intra-uterine chronic exposure to DTZ has a large and prolonged effect on newborn metabolism deacetylase activity compared with the unexposed rabbit.
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Affiliation(s)
- L J Fraile
- Department of Pharmacology, Faculty of Veterinary Science, University of Zaragoza, Spain
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Hendriks MG, Dogterom P, Ebels JT, Oosterhuis B, Geertsema LR, Hulot T, Bianchetti G, Jonkman JH. A study comparing biopharmaceutic characteristics of four once daily controlled release diltiazem preparations. Fundam Clin Pharmacol 1998; 12:559-65. [PMID: 9794155 DOI: 10.1111/j.1472-8206.1998.tb00986.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the present study we have compared the steady state biopharmaceutic characteristics of four diltiazem once daily controlled release capsules: Mono-Tildiem LP 300 (300 mg), Adizem XL (300 mg), Cardizem (300 mg) and Dilacor (240 mg). Sixteen healthy male volunteers (aged 22.9 +/- 3.3 years, range 19-31 years) completed an open label, multiple oral dose, randomized, four-period crossover study without a washout period in between. The volunteers received each diltiazem formulation once daily for four days. Trough diltiazem and metabolites plasma concentrations were determined on days 3 and 4. The 24-h plasma concentration-time profiles were assessed after the dose on day 4 of each period. The following steady state pharmacokinetic parameters for diltiazem were calculated: the minimum plasma concentration (cmin), the maximum plasma concentration (cmax), the time to reach that concentration (tmax), the time interval during which the plasma concentration exceeds 50% of cmax (t50), the area under the plasma concentration-time curve (AUC72-96) and the peak-to-trough fluctuation (PTF). For the metabolites of diltiazem, N-mono-desmethyl-diltiazem (NDM) and desacetyldiltiazem (DAD), AUC72-96 (AUCNDM and AUCDAD) and the ratio metabolite/parent compound were calculated. Steady state was achieved on day 3. Except one, all controlled release formulations have satisfactory controlled release properties allowing once daily administration. However, significant (P < 0.05) differences were found between the pharmacokinetic characteristics which do not allow exchange of the various formulations. Concentrations well below 50 ng.mL-1 in the morning hours were observed for Dilacor (240 mg) and Adizem XL (300 mg), which could be a disadvantage of these formulations as it is well-known that ischaemic events occur at a higher rate during that part of the day. The plasma concentration profiles NDM and DAD, the major circulating metabolites, parallel the plasma concentration profiles for the parent compound. From a clinical point of view, all treatments were well tolerated.
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Affiliation(s)
- M G Hendriks
- Pharma Bio-Research International BV, AE Zuidlaren, The Netherlands
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Garcia MA, Aramayona JJ, Bregante MA, Fraile LJ, Solans C. Simultaneous determination of verapamil and norverapamil in biological samples by high-performance liquid chromatography using ultraviolet detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1997; 693:377-82. [PMID: 9210442 DOI: 10.1016/s0378-4347(97)00058-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this paper we develop an high-performance liquid chromatographic method with ultraviolet detection for the determination of verapamil and its primary metabolite norverapamil in biological samples. Both compounds, as well as the internal standard, imipramine, were extracted from alkalinised blood, with n-hexane-isobutyl alcohol, back-extracted into 0.01 M phosphoric acid and determined using a reversed-phase column and ultraviolet monitoring at 210 nm. The average coefficient of variation obtained over the concentration range of 1-1000 ng/ml is about 3%. The detection limit is below 5 ng/ml for both compounds, and extraction recoveries close to 80%. The method was applied to a pharmacokinetic study of the drug and its active metabolite and used to analyse blood samples from verapamil treated rabbits.
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Affiliation(s)
- M A Garcia
- Department of Analytical Chemistry, Veterinary Faculty, University of Zaragoza, Spain
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Johnson LM, Atkins CE, Keene BW, Bai SA. Pharmacokinetic and pharmacodynamic properties of conventional and CD-formulated diltiazem in cats. J Vet Intern Med 1996; 10:316-20. [PMID: 8884718 DOI: 10.1111/j.1939-1676.1996.tb02069.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The i.v. and apparent steady-state kinetics of diltiazem HCI (DLT) and slow-absorption long-acting diltiazem (CD) given p.o. were investigated in cats. The effects of p.o. diltiazem on heart rate and PR interval were also studied. Plasma diltiazem concentrations were determined by ultraviolet high-performance liquid chromatography (UV-HPLC), using verapamil as the internal standard. Heart rate and PR interval determinations were evaluated over a 24-hour period for the PO formulations and compared with values under diltiazemfree conditions. The mean systemic clearance and apparent volume of distribution of i.v. diltiazem were 15.0 mL/min/kg and 2.70 L/kg, respectively. The elimination half-life of diltiazem after i.v. and p.o. DLT administration were approximately 120 minutes. In contrast, the terminal half-life of CD was 460 minutes. The mean apparent bioavailability of DLT p.o. was 71%, which was significantly higher than that observed with CD (36%). Heart rate and PR intervals in cats receiving the 2 formulations at steady-state were not different from those measured in the drug-free state. We conclude that DLT at 1 mg/kg p.o. tid and CD at 10 mg/kg p.o. sid provide plasma concentrations that are known to have pharmacodynamic effects in other species.
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Affiliation(s)
- L M Johnson
- Department of Anatomy, Physiological Sciences, and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA
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Maskasame C, Lankford S, Bai SA. The effects of chronic oral diltiazem and cimetidine dosing on the pharmacokinetics and negative dromotropic action of intravenous and oral diltiazem in the dog. Biopharm Drug Dispos 1992; 13:521-37. [PMID: 1489943 DOI: 10.1002/bdd.2510130706] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The kinetics and negative dromotropic action of intravenous (1 mg kg-1) and oral (5 mg kg-1) diltiazem were studied in dogs after acute doses, after treatment for 3 days with oral diltiazem (5 mg kg-1, t.i.d.), and after 3 days' treatment with oral diltiazem (5 mg kg-1 t.i.d.) and cimetidine (200 mg t.i.d.). Plasma concentrations of diltiazem and two of its metabolites, desacetyldiltiazem and desmethyldiltiazem were measured by HPLC. Chronic oral dosing significantly lowered both the systemic and oral clearance of diltiazem, with no changes in either the volume of distribution or blood binding of diltiazem. Cimetidine treatment resulted in a significant reduction in diltiazem oral clearance from chronic control with no effect on its systemic clearance. The AUCs of both metabolites increased by greater than threefold from acute to chronic oral dosing; however, the ratio of each metabolite's AUC to that of diltiazem AUC was not significantly altered. Cimetidine treatment significantly lowered these ratios. The negative dromotropic potency of diltiazem after the acute oral dose was three times greater than that after intravenous or chronic control dosing. Cimetidine treatment resulted in further lowering chronic oral diltiazem potency. These data indicate that the disposition and negative dromotropic action of diltiazem is dependent both on the route of administration and the duration of treatment, and can be altered by co-administration with cimetidine.
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Affiliation(s)
- C Maskasame
- Department of Anatomy, College of Veterinary Medicine, North Carolina State University, Raleigh 27606
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20
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Laflamme AK, Caillé G, Cardinal R, Croteau D, Lamoureux C, Lambert C. Effect of congestive heart failure on clentiazem pharmacokinetics in a dog model. Biopharm Drug Dispos 1992; 13:513-20. [PMID: 1489942 DOI: 10.1002/bdd.2510130705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Clentiazem, 8-chloro diltiazem, is a calcium channel blocker currently undergoing evaluation for the treatment of stable angina and hypertension. As patients with ischaemic disorders often present some degree of heart failure, the aim of this study was to investigate the effect of congestive heart failure on clentiazem (200 micrograms kg-1, i.v. bolus) pharmacokinetics in a canine model. Congestive heart failure was induced in six dogs by rapid ventricular pacing (240 beats min-1) for 3-5 weeks. Clentiazem pharmacokinetics was studied in each dog under the control condition and after the development of clinical signs of heart failure (ascites, dyspnea, fatigue). Blood samples were collected up to 480 min post-dose. Clentiazem plasma concentrations were determined by high performance liquid chromatography. The area under the plasma concentration versus time curves (AUC0-infinity) was significantly increased in congestive heart failure dogs (8.8 +/- 1.6 vs 21.8 +/- 1.4 micrograms min ml-1) (mean +/- SEM). These changes were related to a reduction of the volume of distribution of the central compartment (0.9 +/- 0.1 vs 0.2 +/- 0.11 kg-1) and total body clearance (1.9 +/- 0.4 vs 0.7 +/- 0.21 h-1 kg-1). It is concluded that, in our model, congestive heart failure significantly modifies clentiazem disposition. These results suggest that caution should be exercised when clentiazem is given to patients with a low ejection fraction and a compromised cardiac function. Reduced loading and maintenance doses might be recommended in patients with severe congestive heart failure.
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Affiliation(s)
- A K Laflamme
- Research Centre, Hôpital du Sacré-Coeur de Montréal, Canada
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21
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Christrup LL, Bonde J, Rasmussen SN, Sonnergaard JM, Jensen BH. Single-dose and steady-state pharmacokinetics of diltiazem administered in two different tablet formulations. PHARMACOLOGY & TOXICOLOGY 1992; 71:305-7. [PMID: 1454755 DOI: 10.1111/j.1600-0773.1992.tb00989.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Single-dose and steady state pharmacokinetics of diltiazem administered in two different oral formulations were assessed with particular reference to rate and extent of absorption. Following single dose administration a significant difference in tmax was observed (2.9 +/- 1.9 and 6.8 +/- 2.6 hr respectively) whereas differences in AUC, t1/2 and Cmax were not significant. The AUC (mean +/- S.D.) values following single dose administration of Cardil and Cardizem were 678.4 +/- 321.5 and 948.6 +/- 580.6 ng.ml-1.hr respectively. The mean and the 95% confidence limits for the observed ratio AUCCardil/AUCCardizem are 0.89 and 0.44-1.34 respectively. At steady-state a significant difference between Cmax/Cmin and tmax was seen Cmax/Cmin being 4.9 and 3.2 respectively and Tmax being 2.7 +/- 2.0 and 6.0 +/- 2.8 hr respectively, whereas Cmax and AUC did not differ significantly. The AUC (mean +/- S.D.) values in steady state of Cardil and Cardizem were 880.1 +/- 399.8 and 1056.8 +/- 509.8 ng.ml-1.hr respectively. The mean and the 95% confidence limits for the observed ratio AUCCardil/AUCCardizem are 0.96 and 0.66-1.26 respectively. Although the observed ratios AUCCardil/AUCCardizem in both the single-dose and the steady-state study do not differ significantly from 1.0, the confidence limits exceed the acceptable values given by Poulsen & Juul (personal communication 1990) (a 20% decrease or increase of the ratio to 0.8 or 1.2).
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Affiliation(s)
- L L Christrup
- Department of Pharmaceutics, Royal Danish School of Pharmacy, Copenhagen
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22
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Abstract
The efficacy and safety of once-daily doses of 200, 300, and 400 mg of bepridil hydrochloride were compared with placebo in a 14-week multi-center, double-blind parallel study. All doses of bepridil significantly reduced weekly anginal attacks and nitroglycerin consumption from baseline levels. Bepridil also significantly improved total exercise time, time to angina, time to 1 mm ST-segment depression, and total work. Reduction in heart rate (maximum mean decreases of 7-8 beats/min) and prolongation of QT and corrected QT (QTc) intervals were associated with bepridil therapy. Bepridil was well tolerated; most adverse reactions reported were mild and tolerable even at the 400-mg dose. This study provides strong support for the use of bepridil in patients with chronic stable angina pectoris that is not optimally controlled by other available antianginal therapies. A double-blind withdrawal study is also reported, in which patients stabilized on bepridil were randomized to either continue on bepridil therapy or receive placebo. Patients who were withdrawn from bepridil therapy showed significant increases in the number of weekly anginal attacks and nitroglycerin consumption compared with levels seen during long-term treatment. Patients withdrawn from bepridil therapy showed significant deterioration in exercise tolerance compared with baseline and with those maintained on bepridil.
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Affiliation(s)
- W Shapiro
- University of Texas Southwestern Medical Center, Dallas
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23
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Abstract
Verapamil was the first calcium-channel blocker (CCB). It has been used since 1962 in Europe then in Japan for its antiarrhythmic and coronary vasodilator effects. The CCB have become prominent cardiovascular drugs during the last 15 years. Many experimental and clinical studies have defined their mechanism of action, the effects of new drugs in this therapeutic class, and their indications and interactions with other drugs. Due to the large number of patients treated with CCB it is important for the anaesthetist to know the general and specific problems involved during the perioperative period, the interactions with anaesthetics and the practical use of these drugs.
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Affiliation(s)
- P G Durand
- Department of Anaesthesia and Intensive Care, Hôpital Cardio-vasculaire et Pneumologique, Lyon, France
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24
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Chaves das Neves HJ, Gomes da Silva MD, Rocha MP. Bioequivalence assessment of diltiazem preparations by means of discriminant analysis of data from solid-phase extraction and liquid chromatography. J Pharm Biomed Anal 1991; 9:941-7. [PMID: 1822216 DOI: 10.1016/0731-7085(91)80027-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A solid-phase extraction technique for sample clean-up coupled with a new LC procedure is reported for the assay of diltiazem in plasma. The use of disposable cartridges provides selective extraction and easy automation. A new LC system based on LiChrospher RP 60 Select B columns is described. For routine analysis, the procedure provides a rapid simultaneous clean-up of several samples prior to chromatography and reproducible recoveries over a concentration range of 10-800 ng. The procedure was used to analyse the plasma samples from a bioequivalence study of three commercial diltiazem preparations. The pharmacokinetic parameters in 12 healthy male volunteers were determined and the assessment of bioequivalence was conducted by discriminant analysis.
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Affiliation(s)
- H J Chaves das Neves
- Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, Monte da Caparica, Portugal
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25
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Zachariah PK, Moyer TP, Theobald HM, Frantz RP, Kurtz SB, McCarthy JT, Smith RL. The pharmacokinetics of racemic verapamil in patients with impaired renal function. J Clin Pharmacol 1991; 31:45-53. [PMID: 2045528 DOI: 10.1002/j.1552-4604.1991.tb01885.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The pharmacokinetics of verapamil were studied in patients with renal failure who were undergoing maintenance hemodialysis and in normal subjects after an IV infusion of 10 mg and a single oral dose of 120 mg. Plasma levels of verapamil and its active metabolite, norverapamil, were analyzed by a sensitive and specific HPLC procedure. Severe renal failure requiring hemodialysis did not change the time course of verapamil and norverapamil plasma concentrations after either the IV or oral dose. The terminal elimination rate constant, clearance, volume of distribution, and bioavailability of verapamil were not significantly different between the two groups of subjects. In addition, the apparent maximal plasma concentration, terminal elimination rate constant, and area under the curve for norverapamil were similar in patients with renal failure and normal subjects. The study showed that the plasma disposition of verapamil and norverapamil was not affected in patients with impaired renal function. Furthermore, this study does not indicate that any change in dosage is necessary when single doses of verapamil are administered to patients with renal failure.
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Affiliation(s)
- P K Zachariah
- Division of Hypertension and Internal Medicine, Mayo Clinic, Rochester, MN 55905
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26
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Cotting J, Reichen J, Kutz K, Laplanche R, Nüesch E. Pharmacokinetics of isradipine in patients with chronic liver disease. Eur J Clin Pharmacol 1990; 38:599-603. [PMID: 2142648 DOI: 10.1007/bf00278589] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The pharmacokinetics of the dihydropyridine calcium antagonist isradipine has been examined in 8 healthy volunteers, 7 patients with non-cirrhotic chronic liver disease (CLD), and 8 patients with biopsy-proven cirrhosis (CIR). Isradipine was simultaneously given orally (12C 5 mg) and i.v. (13C 1 mg). Systemic availability was significantly increased from 17% to 16% in controls and CLD, respectively, to 37% in CIR. The corresponding systemic clearances averaged 1.1, 0.9 and 0.6 l.min-1, the reduction in cirrhotics being significant. Both aminopyrine demethylation capacity, a measure of hepatic microsomal function, and indocyanine green disappearance, a measure of hepatic perfusion, were correlated with the reduction in systemic clearance, and the reduction in oral clearance was correlated with the reciprocal of the serum bile acid concentration. The loss of first-pass extraction should be considered when this calcium antagonist is given perorally in patients with hepatic cirrhosis.
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Affiliation(s)
- J Cotting
- Department of Clinical Pharmacology, University of Berne, Switzerland
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27
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Husum D, Johnsen A, Jensen G. Requirements for drug monitoring of verapamil: experience from an unselected group of patients with cardiovascular disease. PHARMACOLOGY & TOXICOLOGY 1990; 66:163-9. [PMID: 2333271 DOI: 10.1111/j.1600-0773.1990.tb00726.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Serum verapamil and metabolite concentrations were determined by HPLC in 29 patients in routine treatment with verapamil, and 23 were in steady state. Dosage levels and corresponding mean trough levels (+/- S.D.) were as follows: 120 mg daily: 79.1 (+/- 77) nmol/l, 240 mg daily: 173.3 (+/- 200.1) nmol/l, 360 mg daily: 204 (+/- 110.2) nmol/l and 480 mg daily: 361.0 (+/- 231.4) nmol/l. The variation coefficients were 97.3, 115.4, 54.0, and 62.1, respectively, thus showing considerable interpatient variation. Repeated determination of trough levels showed, in contrast, only small intrapatient variation (variation coefficient 35.8, 1.9, and 7.4, at the dosage levels 120, 240 and 340 mg per day). No significant correlation was found between serum verapamil levels age, sex, or weight. No significant effect of digoxin on the concentration of serum verapamil was found. No relation was observed between serum verapamil concentrations and desired effect or side-effects. Two patients showed no measurable serum verapamil, but one of these had detectable levels of metabolites. Such patients may represent subgroups of fast metabolizers or non-absorbers. Measurements of the metabolites nor-verapamil, D 620 and D 617 indicated saturation of the first-pass metabolism. In conclusion, therapeutic drug monitoring is not indicated during routine verapamil treatment, whereas single measurements of verapamil may be warranted in patients not responding to treatment in order to identify fast metabolizers or non-absorbers.
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Affiliation(s)
- D Husum
- Department of Cardiology, University of Copenhagen, Hvidovre Hospital, Denmark
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28
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Ververs FF, Schaefer HG, Lefevre JF, Lopez LM, Derendorf H. Simultaneous assay of propranolol, diltiazem and metabolites of diltiazem in human plasma by liquid chromatography. J Pharm Biomed Anal 1990; 8:535-9. [PMID: 2093390 DOI: 10.1016/0731-7085(90)80064-v] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- F F Ververs
- College of Pharmacy, Department of Pharmaceutics, Hillis Miller Health Center, University of Florida, Gainesville 32610
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29
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Abrams WB. Introduction. J Am Geriatr Soc 1989. [DOI: 10.1111/j.1532-5415.1989.tb02242.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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30
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SCHWARTZ J. CALCIUM ANTAGONISTS, A NEW CLASS OF ANTIHYPERTENSIVE AGENTS. Fundam Clin Pharmacol 1988. [DOI: 10.1111/j.1472-8206.1988.tb00662.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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31
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Affiliation(s)
- W M Bennett
- Division of Nephrology and Hypertension, Oregon Health Sciences University, Portland
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32
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Abstract
The mechanism of action of Ca++ antagonists remains debatable. Not all voltage-sensitive calcium channels have the same sensitivity to organic calcium blockers. Those in smooth muscle are clearly more sensitive than those in heart, and at least some of those in brain are not blocked at all. It is possible that in vascular smooth muscle, calcium antagonists act essentially on receptor-operated channels. In any case, calcium antagonists are potent antihypertensive agents, but in clinical practice they have limitations. A second generation of dihydropyridines may provide a higher degree of therapeutic selectivity.
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33
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Jensen HK, Nielsen-Kudsk F. Pharmacokinetics and dynamic effects of diltiazem in the isolated guinea-pig heart. PHARMACOLOGY & TOXICOLOGY 1988; 62:166-71. [PMID: 3375187 DOI: 10.1111/j.1600-0773.1988.tb01866.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Myocardial pharmacokinetics of diltiazem showed two-compartment characteristics in the isolated, spontaneously beating guinea-pig heart. Half-times of initial and terminal drug accumulation phases were about 2.1 and 14.4 min., respectively. At 1 microgram ml-1 (2.4 microM) in the perfusion liquid the average concentration of diltiazem in the myocardium at steady state was about 16 micrograms g-1 (38.6 microM) with 17% referable to the deepest, possibly intracellular compartment. Increasing diltiazem concentrations from 13 to 889 ng ml-1 (31-2144 nM) produced a progressive increase in coronary flowrate from 100 to 174%. The computed Em- and EC50-values were 73.2% and 187 nM, respectively. Oxygen consumption decreased to 27.6% showing Em = 106% and IC50 = 1536 nM. Amplitude and velocity of myocardial contraction decreased to about 6% and 2%; Em = 101% and 104%, IC50 = 266 and 186 nM, respectively. Heart beating frequency decreased to 63% exhibiting Em = 58% and IC50 = 2015 nM. The PQ- and QRS-intervals increased to 133% and 112%, respectively. The frequency-corrected QT-interval decreased to 81.6%. Our findings demonstrate a relatively rapid and moderate accumulation of diltiazem in the guinea-pig heart accompanied by a marked increase in coronary flow, progressive and pronounced negative inotropic and chronotropic effects and a less than proportional decrease in oxygen consumption.
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Affiliation(s)
- H K Jensen
- Institute of Pharmacology, University of Aarhus, Denmark
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34
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Adnet P, Krivosic-Horber R. [Calcium inhibitors and anesthesia]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 1988; 7:494-505. [PMID: 2975926 DOI: 10.1016/s0750-7658(88)80088-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Calcium blockers (CB) are routinely used. This could lead to possible interference with anaesthetic drugs. CB prevent calcium from entering the cell by inhibiting the slow voltage-dependent calcium channels. They act mostly on heart and smooth muscle. Of all the possible indications, the three that are confirmed are coronary heart disease, arterial hypertension and supraventricular rhythm disturbances. Most of the work published and the cases reported concerns interactions between CB and halogenated anaesthetic agents; the latter's actions on the heart depend on cellular calcium exchange. Also, the cardiovascular effects of these anaesthetics are similar to that of CB. Experimentally, halothane and enflurane have direct cardiac inhibitory effects similar to verapamil and diltiazem, whereas isoflurane's properties seem closer to the dihydropyridines (nifedipine and nicardipine). Giving verapamil or diltiazem increases the number of sino-atrial and atrio-ventricular blocks when using a halogenated agent. Clinically, interpreting the effects of CB during anaesthetic induction is difficult because of the pathology (coronary heart disease, cardiac failure), the other drugs (beta-blockers and nitrates) and the type of anaesthesia (emergency or elective). Interactions can give rise to anything from a severe cardiovascular collapse, requiring catecholamines, to a mild fall in blood pressure which responds well to plasma expansion, or even no effect on blood pressure. Rebound is seen on stopping CB in patients with coronary heart disease or arterial hypertension; stopping them before surgery does not therefore seem justified. However, extreme care must be taken when using halogenated agents for patients under treatment with CB and/or beta-blockers. A wary anaesthetist will be able to adapt the technique to the patient. It has been suggested that CB could be used to treat preoperatively myocardial ischaemia (diltiazem), hypertensive crises (nifedipine, nicardipine) and ventricular rhythm disturbances (verapamil); this must be done with caution, the patient being closely monitored (haemodynamic and electrocardiographic monitoring). Postoperatively, intranasal nifedipine, continuous intravenous nicardipine or diltiazem have been used to treat increases in arterial blood pressure during recovery and to adapt the cardiovascular system to the increased metabolic needs. Here again, close patient monitoring is essential. In any case, treatment with CB which has been stopped should be started up again as soon as possible.
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Affiliation(s)
- P Adnet
- Département d'Anesthésie-Réanimation Chirurgicale I, Hôpital B, Centre Hospitalier Universitaire, Lille
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35
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Isanta JR, Lasheras B, Fos D, Cenarruzabeitia E. Comparative diltiazem plasma clearance in normotensive and hypertensive rats. J Pharm Sci 1987; 76:862-5. [PMID: 3440927 DOI: 10.1002/jps.2600761203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Diltiazem plasma clearance was studied in normotensive (NR) and spontaneous hypertensive rats (SHR), either following intravenous bolus administration of 3 mg/kg (CLiv), or after 25 min of intravenous infusion (CL25) at different dose levels (1, 2, 4, and 8 mg/kg/30 min in NR; 0.5, 1, 2, and 4 mg/kg/30 min in SHR). The diltiazem pharmacokinetic profile fit a two-compartment open model better, both in NR and SHR. The CLiv of diltiazem was significantly higher in NR than in SHR. Following infusion, diltiazem plasma clearance increased for high levels of infused dose in NR and in SHR. For each level of dose, CI25 was significantly higher in NR than in SHR. For both groups of animals, CI25 values were significantly higher than their respective CIiv values. These results show the influence of hypertension on the pharmacokinetic characteristics of diltiazem, as well as the effect of its own vasodilator action. An increase in diltiazem clearance values may be due to an increase in hepatic blood flow that is a result of its vasodilator action.
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Affiliation(s)
- J R Isanta
- Department of Pharmacology, Universidad de Navarra, Pamplona, Spain
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36
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Homeida MM, Ali HM, Arbab BM, Harron DW. Propranolol disposition in patients with hepatosplenic schistosomiasis. Br J Clin Pharmacol 1987; 24:393-6. [PMID: 3663453 PMCID: PMC1386264 DOI: 10.1111/j.1365-2125.1987.tb03187.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Eight Sudanese patients with hepatosplenic schistosomiasis and seven Sudanese controls were administered a single oral dose of long acting (LA), propranolol 160 mg; blood propranolol levels were measured at regular intervals for 12 h using g.l.c. In patients with hepatosplenic schistosomiasis, propranolol blood concentrations were greater (P less than 0.05) at all time intervals, Cmax 63.5 (29-143) ng ml-1 (median and range) than controls Cmax 23 (12-37) ng ml-1. Median AUC0-12 was also greater (P less than 0.05) (533 and 218 ng ml-1 h respectively), tmax were not significantly different. In patients and controls prior to treatment, standing heart rate (77.5 (60-110), 72 (68-74) beats min-1) systolic (120 (105-150), 110 (100-120) mm Hg) and diastolic blood pressure (75 (60-90), 70 (60-80) mm Hg) were not significantly different. However following propranolol administration a reduction (P less than 0.05) occurred in both systolic (median 20 mm Hg) and diastolic (median 12.5 mm Hg) blood pressure in the patients compared with controls. Heart rate was reduced by a median of 10 beats min-1 in both groups. These observations indicate that propranolol bioavailability in patients with hepatosplenic schistosomiasis is increased possibly due to reduced presystemic extraction.
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Affiliation(s)
- M M Homeida
- Department of Medicine, University of Khartoum, Sudan
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37
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Tse FL, Jaffe JM. Pharmacokinetics of PN 200-110 (isradipine), a new calcium antagonist, after oral administration in man. Eur J Clin Pharmacol 1987; 32:361-5. [PMID: 2956112 DOI: 10.1007/bf00543970] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The pharmacokinetics of PN 200-110 (isradipine), a new calcium channel blocking agent, have been studied in 18 normal male volunteers who received orally a single 5-mg dose, a single 20-mg dose, or repeated administration of 5 mg every 8 h for 13 doses of [14C]PN 200-110. PN 200-110 was rapidly and almost completely (90-95%) absorbed from the gastrointestinal tract, although the estimated bioavailability was only 17% due to extensive first-pass metabolism. The pharmacokinetics of PN 200-110 appeared to be linear in the 5 to 20-mg dose range, as indicated by the dose-proportional blood levels of total radioactivity as well as the parent drug. Absorbed PN 200-110 was completely metabolized prior to excretion. The recovery of radioactivity after both the 5 and the 20-mg dose was virtually complete within the experimental period, with a renal:fecal excretion ratio of ca. 70:30. Repeated administration of [14C]PN 200-110 showed no change in pharmacokinetic characteristics. During the 5 mg thrice daily regimen, steady-state blood levels of parent drug were reached in 2 days while those of total radioactivity were reached in approximately 4 days. PN 200-110 and total radioactivity accumulated in blood by a factor of 2.1 and 3.4, respectively, indicating effective half-lives of 8.8 h and 16 h. The oral administration of [14C]PN 200-110 prescribed in the present study was safe and well tolerated.
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38
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Mooy J, Böhm R, van Baak M, van Kemenade J, vd Vet A, Rahn KH. The influence of antituberculosis drugs on the plasma level of verapamil. Eur J Clin Pharmacol 1987; 32:107-9. [PMID: 3582463 DOI: 10.1007/bf00609969] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The influence of antituberculosis drugs on the plasma level of verapamil was studied after its oral and intravenous administration. Six patients who had been treated for at least 6 months with a combination of rifampicin, ethambutol and isoniazid received a single oral dose of 40 mg verapamil. As compared to untreated subjects, the antituberculosis drugs greatly reduced the bioavailability of the calcium antagonist. Studies in patients in whom treatment with ethambutol and isoniazid had been discontinued revealed that the effect was due to rifampicin. The drugs for tuberculosis had no influence on the plasma level of verapamil when it was given intravenously. The findings can be explained by the induction of verapamil metabolizing liver enzymes in patients treated with rifampicin.
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39
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Ellenbogen KA, Roark SF, Smith MS, McCarthy EA, Bjornsson TD, Pritchett EL. Effects of sustained intravenous diltiazem infusion in healthy persons. Am J Cardiol 1986; 58:1055-60. [PMID: 3776858 DOI: 10.1016/0002-9149(86)90114-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A 3-stage infusion of diltiazem was tested in 8 subjects for up to 48 hours: a bolus injection (10 mg over 3 minutes), a rapid loading infusion (20 mg over 30 minutes) and a maintenance infusion (10 mg/hour to the end of the study). This regimen produced stable median plasma diltiazem concentrations of approximately 150 ng/ml. The median half-life of elimination for diltiazem was 206 minutes (range 144 to 452) and median total clearance was 980 ml/min (range 665 to 1,907). The PR interval lengthened 10 to 18% during the maintenance infusion in 7 subjects; in 1 subject atrioventricular nodal Wenckebach conduction was recorded during the rapid loading infusion. Systolic blood pressure decreased from 124 +/- 7 mm Hg (mean +/- standard deviation) during the control period to 121 +/- 8 mm Hg during the rapid loading infusion (p = 0.03 compared with control) and to 117 +/- 7 mm Hg (p = 0.04 compared with control) during the maintenance infusion. Heart rate did not change. PR interval and blood pressure returned to control levels within 4 hours after the infusion was stopped. Loading and maintenance infusion may be an attractive method of administering diltiazem when stable drug concentrations are required for prolonged periods.
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Eikenburg DC, Lokhandwala MF. Calcium antagonists and sympathetic neuroeffector function. JOURNAL OF AUTONOMIC PHARMACOLOGY 1986; 6:237-55. [PMID: 2876996 DOI: 10.1111/j.1474-8673.1986.tb00650.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Hoon TJ, Bauman JL, Rodvold KA, Gallestegui J, Hariman RJ. The pharmacodynamic and pharmacokinetic differences of the D- and L-isomers of verapamil: implications in the treatment of paroxysmal supraventricular tachycardia. Am Heart J 1986; 112:396-403. [PMID: 3526855 DOI: 10.1016/0002-8703(86)90281-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
There is increasing interest in defining the pharmacodynamic and pharmacokinetic characteristics of drugs that are marketed as racemic mixtures. Verapamil is one such drug that is commercially available as a mixture of D- and L-isomers. The L-isomer of verapamil has a greater-negative inotropic, negative chronotropic, and negative dromotropic potency than the D-isomer. The values for fraction unbound in serum, distribution volume, and systemic clearance are substantially greater for the L-isomer after intravenous dosing. After oral dosing, the D-isomer achieves peak plasma concentrations five times greater than the L-isomer. The pharmacodynamic and pharmacokinetic characteristics of each isomer are reviewed. The differences in the concentrations of the D- and L-isomers after oral vs intravenous dosing may contribute to the relatively lower efficacy of orally administered verapamil in the treatment of PSVT.
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Roth A, Harrison E, Mitani G, Cohen J, Rahimtoola SH, Elkayam U. Efficacy and safety of medium- and high-dose diltiazem alone and in combination with digoxin for control of heart rate at rest and during exercise in patients with chronic atrial fibrillation. Circulation 1986; 73:316-24. [PMID: 3943166 DOI: 10.1161/01.cir.73.2.316] [Citation(s) in RCA: 115] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We evaluated the efficacy and the safety of medium-(240 mn/day) and high-dose (360 mg/day) diltiazem alone and in combination with digoxin when used for control of heart rate in 12 patients with chronic atrial fibrillation. Medium-dose diltiazem was comparable to therapeutic dose of digoxin at rest (88 +/- 19 vs 86 +/- 12 beats/min) but superior during peak exercise (154 +/- 23 vs 170 +/- 20 beats/min; p less than .05). High-dose diltiazem resulted in better control of heart rate than digoxin both at rest (79 +/- 17 beats/min; p less than .05) and exercise (136 +/- 25 beats/min; p less than .05) but was associated with side effects in 75% of the patients. Combined therapy of digoxin and diltiazem enhanced the effect of digoxin alone and resulted in significantly better control of heart rate at rest (67 +/- beats/min with medium-dose and 65 +/- beats/min with high-dose diltiazem) and during peak exercise (132 +/- 32 and 121 +/- 24 beats/min, respectively). However, the difference in heart rate between these two doses was not significant. Reduction of heart rate combined with concomitant effect on blood pressure resulted in a significant fall in pressure-rate product at rest from 10,077 +/- 1708 mm Hg/min on digoxin alone to 7877 +/- 1818 mm Hg/min after the addition of medium-dose diltiazem (p less than .05) and during exercise form 25,670 +/- 3606 to 18,439 +/- 4115 mm Hg/min (p less than .05). Continued therapy with digoxin combined with diltiazem 240 mg/day for 21 +/- 8 days in nine patients showed persistent effect on heart rate and blood pressure without any toxic manifestations or change in serum digoxin (1.5 +/- 0.4 vs 1.3 +/- 0.4 ng/ml) or plasma diltiazem concentrations (204 +/- 72 vs 232 +/- 129 ng/ml). In conclusion, medium-dose diltiazem when combined with digoxin is an effective and safe regimen for the treatment of patients with chronic atrial fibrillation and enhances digoxin-mediated control of heart rate both at rest and during exercise.
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Rétamal O, Coriat P, Pamela F, Godet G, Bertrand M, Viars P. [Prevention of hypertensive attacks after carotid surgery. The value of nifedipine and diltiazem]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 1986; 5:278-86. [PMID: 3777553 DOI: 10.1016/s0750-7658(86)80157-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A randomized study was carried out to determine whether postoperative administration of either intranasal nifedipine or intravenous diltiazem was effective in preventing hypertensive episodes after carotid endarterectomy. Sixty-three consecutive patients undergoing this surgery were randomly assigned to three groups (n = 21): control (C), nifedipine (N) and diltiazem (D). Anaesthesia was induced with flunitrazepam (0.02 mg X kg-1), fentanyl 6 micrograms X kg-1 and pancuronium (0.1 mg X kg-1), and maintained by N2O/O2 (50%), additional fentanyl and halothane or enflurane when warranted. Postoperatively, patients were warned whilst under mechanical ventilation in a recovery room. Upon arrival in the recovery room, intranasal nifedipine (10 mg) was given to patients included in group N, while patients from group D received an intravenous dose of 0.3 mg X kg-1 of diltiazem, followed by a continuous infusion of 3 micrograms X kg-1 X min-1 until 15 min after extubation. No preventive treatment was given to patients in group C. If postoperative systolic blood pressure rose to more than 180 mmHg, 10 mg of nifedipine were administered intranasally. During the postoperative period, 13 patients from group C, 5 from group N and 4 from group D exhibited hypertensive episodes (systolic blood pressure greater than 180 mmHg or diastolic blood pressure greater than 100 mmHg). Intranasal administration of 10 mg nifedipine led to the normalization of blood pressure in 20 out of these 22 patients. This study confirmed the high incidence of hypertensive attacks after carotid endarterectomy, and showed that prophylactic administration of nifedipine or intravenous diltiazem was highly effective in preventing such hypertensive episodes.
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Marvola M, Kannikoski A, Taskinen J, Ottoila P. Assessment of bioavailability of experimental single-unit sustained release tablets of verapamil hydrochloride using the stable isotope technique. J Pharm Pharmacol 1985; 37:766-70. [PMID: 2867156 DOI: 10.1111/j.2042-7158.1985.tb04965.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A stable isotope technique has been used to assess the bioavailability of sustained release verapamil products. The test formulations were tablets with a core containing 90 mg of verapamil hydrochloride coated with ethylcellulose film, the permeability of which was controlled using different amounts of hydroxypropyl methylcellulose. A product containing ethylcellulose 75% hydroxypropyl methylcellulose 25% w/w gave a single-unit sustained release tablet of verapamil hydrochloride that allowed a dose interval of 24 h. There was no loss in bioavailability, even though verapamil had extensive first-pass metabolism.
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Mooy J, Schols M, v Baak M, v Hooff M, Muytjens A, Rahn KH. Pharmacokinetics of verapamil in patients with renal failure. Eur J Clin Pharmacol 1985; 28:405-10. [PMID: 4029246 DOI: 10.1007/bf00544358] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The pharmacokinetics of verapamil was studied in patients with end-stage chronic renal failure and in normal subjects after i.v. injection of 3 mg and a single oral dose of 80 mg. Plasma levels of verapamil and its active metabolite norverapamil were measured by HPLC. After i.v. injection, the terminal phase half-life and total plasma clearance of verapamil in both groups were similar. Haemodialysis did not change the time course of plasma verapamil levels after i.v. administration. After a single oral dose, the plasma levels of verapamil and norverapamil in both groups of subjects were similar. Subsequently, normal volunteers and patients with renal failure were treated for 5 days with oral verapamil 80 mg t.d.s. There was no difference between the 2 groups of subjects in the trough and peak levels of verapamil or of norverapamil. Intravenous and oral administration of the calcium channel blocking agent had similar effects on blood pressure, heart rate and the PR-interval in the electrocardiogram in both groups. The study demonstrated that the disposition of verapamil was similar in normal subjects and in patients with renal failure.
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Abstract
The effects of diltiazem in rat tail arteries and guinea-pig vasa deferentia have been investigated. Superfusion of the rat tail artery with diltiazem (10(-6) - 10(-4) M) resulted in a dose-related increase in 3H-overflow (P less than 0.001) both in Wistar Kyoto (WKY) and in spontaneously hypertensive (SHR) rats. Release of 3H by transmural stimulation (1 Hz, 2 ms, 10 V) was also much greater in vessels perfused with diltiazem; this effect was dose-dependent. Diltiazem did not significantly alter the proportion of noradrenaline and its metabolites in 3H-overflow, as analysed by column chromatography. In the vasa deferentia of guinea-pigs, diltiazem (10(-9) - 10(-5) M) increased spontaneous 3H-release. The results indicate that diltiazem acts on sympathetic nerves and causes the release of noradrenaline.
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Mattila J, Mäntylä R, Taskinen J, Männistö P. Pharmacokinetics of sustained-release verapamil after a single administration and at steady state. Eur J Drug Metab Pharmacokinet 1985; 10:133-8. [PMID: 3840089 DOI: 10.1007/bf03189707] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Pharmacokinetics of conventional 80 mg tablets and two types of sustained-release (SR) tablets containing 120 and 200 mg of verapamil were compared cross-over in 12 healthy volunteers. Serum concentrations of verapamil and norverapamil were analyzed both after a single oral dose and at steady state after t.i.d. administration of conventional tablets and b.i.d. administration of SR tablets. After 120 mg SR tablets serum concentrations of verapamil usually remained below 100 ng/ml for 5 days. This inadequate bioavailability was caused by very slow absorption. The relative bioavailability of verapamil in 200 mg SR tablets was 93-96% as compared to the conventional tablets. After 200 mg X 2 and 80 mg X 3, the peak serum levels were about 300 and 190 ng/ml, respectively and the trough levels 123-153 and 52-56 ng/ml, respectively. The verapamil/norverapamil ratio varied from 0.69 to 0.84 after a single dose and from 0.8 to 0.93 at steady-state. By the 4th days of treatment, the accumulation ratios ranged between 1.75-2.07 and 1.30-1.75 for verapamil and norverapamil, respectively. For each preparation studied, the apparent Cltot of verapamil was significantly reduced at steady-state. These results show that 200 mg SR verapamil tablets fulfill the basic requirements of retard preparations allowing for twice or even once daily administration.
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Abstract
Bepridil hydrochloride differs from the other calcium antagonists in structure as well as in several clinical pharmacokinetic characteristics. The drug is completely absorbed from the gastrointestinal tract, but first-pass extraction reduces oral bioavailability to approximately 60%. After single-dose administration, the elimination half-life of bepridil averages 33 +/- 15 hours. However, upon multiple dosing, a half-life of 42 +/- 12 hours is found. As with verapamil and diltiazem, bepridil clearance is decreased after multiple dosing. Bepridil is completely metabolized, presumably by hepatic oxidative processes. A total of 17 metabolites have been identified, but the contribution of any of these metabolites to observed clinical response is currently unclear. The free fraction of bepridil in plasma is low, averaging only 0.23%. Despite this high protein binding, in vitro studies indicate that the potential for drug-to-drug interactions based on displacement of bepridil from its binding sites is low. Bepridil follows a linear dose/plasma concentration relation after single and multiple doses of the drug in both healthy volunteers and patients with angina. However, mean steady-state plasma bepridil concentrations are higher in patients, indicating a greater average decreased clearance. Food does not interfere with bepridil absorption. At this time, no significant pharmacokinetic interactions between bepridil and digoxin have been detected.
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Shapiro W, DiBianco R, Thadani U. Comparative efficacy of 200, 300 and 400 mg of bepridil for chronic stable angina pectoris. Am J Cardiol 1985; 55:36C-42C. [PMID: 3919556 DOI: 10.1016/0002-9149(85)90804-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A total of 178 patients participated in a 14-week, multicenter, double-blind, parallel study to evaluate the comparative efficacy and safety of single daily doses of 200, 300 and 400 mg of bepridil hydrochloride and placebo in the treatment of patients with chronic stable angina pectoris. The results showed that weekly angina attacks and nitroglycerin consumption were significantly reduced from baseline levels with all doses of bepridil (p less than 0.01), and the reductions were consistently greater than those in the placebo group. For the 400-mg dose the reductions in angina attacks and nitroglycerin consumption were significantly greater (p less than or equal to 0.05) than those in the placebo group at all but 1 evaluation point. Exercise tolerance improved significantly during bepridil administration (p less than or equal to 0.05), and a significant linear dose response was noted for total exercise time, total work and time to onset of angina. In addition, bepridil was significantly superior to placebo for these parameters at doses of 300 (p less than or equal to 0.05) and 400 mg (p less than or equal to 0.01). There were small reductions in heart rate (mean 3.7 beats/min) and prolongation of QT and QTc intervals (approximately 30 to 40 milliseconds) associated with bepridil treatment. Bepridil was well tolerated by patients in this study. When adverse effects occurred, they most frequently involved the gastrointestinal and central nervous systems. Of the patients receiving bepridil, 6% discontinued therapy because of adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Abstract
Effective use of drugs in therapy depends not only on clinical acumen but also on the availability of relevant pharmacokinetic and pharmacodynamic data. Such information assists in development of safe dosing regimens, prediction of abnormal handling of drugs in states of disease and disorder and anticipation of drug interactions. For the calcium-entry blocking agents now available in the United States (verapamil, nifedipine and diltiazem), these data appeared well after clinical patterns of use evolved. Nonetheless, their relevance continues to be demonstrated by the dependence of each agent on intact liver blood flow and function for normal rates of elimination; by the nonlinear kinetic characteristics for verapamil and diltiazem (and probably for nifedipine, as well) and the derivative implications for decreased dosing frequency requirements; and by observations now appearing on the relation between plasma drug levels and drug effects, both therapeutic and toxic. Such data are discussed herein, with emphasis on those aspects that impact on the clinical use of the calcium-entry antagonists.
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